Design for assembly
Design for assembly (DFA) is a process by which products are designed with ease of assembly in mind. If a product contains fewer parts it will take less time to assemble, thereby reducing assembly costs. In addition, if the parts are provided with features which make it easier to grasp, move, orient and insert them, this will also reduce assembly time and assembly costs. The reduction of the number of parts in an assembly has the added benefit of generally reducing the total cost of parts in the assembly. This is usually where the major cost benefits of the application of design for assembly occur.
Approaches
Design for assembly can take different forms. In the 1960s and 1970s various rules and recommendations were proposed in order to help designers consider assembly problems during the design process. Many of these rules and recommendations were presented together with practical examples showing how assembly difficulty could be improved. However, it was not until the 1970s that numerical evaluation methods were developed to allow design for assembly studies to be carried out on existing and proposed designs.
The first evaluation method was developed at
Starting in 1977, Geoff Boothroyd, supported by an NSF grant at the University of Massachusetts Amherst, developed the Design for Assembly method (DFA), which could be used to estimate the time for manual assembly of a product and the cost of assembling the product on an automatic assembly machine.[2] Recognizing that the most important factor in reducing assembly costs was the minimization of the number of separate parts in a product, he introduced three simple criteria which could be used to determine theoretically whether any of the parts in the product could be eliminated or combined with other parts. These criteria, together with tables relating assembly time to various design factors influencing part grasping, orientation and insertion, could be used to estimate total assembly time and to rate the quality of a product design from an assembly viewpoint. For automatic assembly, tables of factors could be used to estimate the cost of automatic feeding and orienting and automatic insertion of the parts on an assembly machine.
In the 1980s and 1990s, variations of the AEM and DFA methods have been proposed, namely: the GE Hitachi method which is based on the AEM and DFA; the Lucas method, the
Implementation
Most products are assembled manually and the original DFA method for manual assembly is the most widely used method and has had the greatest industrial impact throughout the world.
The DFA method, like the AEM method, was originally made available in the form of a handbook where the user would enter data on worksheets to obtain a rating for the ease of assembly of a product. Starting in 1981, Geoffrey Boothroyd and Peter Dewhurst developed a computerized version of the DFA method which allowed its implementation in a broad range of companies. For this work they were presented with many awards including the
Notable examples
Two notable examples of good design for assembly are the
The IBM Proprinter used design for automated assembly (DFAA) rules. These DFAA rules help design a product that can be assembled automatically by robots, but they are useful even with products assembled by manual assembly.[10]
See also
Notes
- ^ Miyakawa, S. and Ohashi, T., "The Hitachi Assembly Evaluation Method (AEM)," Proc. International Conference on Product Design for Assembly, Newport, Rhode Island, April 15–17, 1986.
- ^ Boothroyd, G., "Design for Assembly – A Designer's Handbook", Department of Mechanical Engineering, University of Massachusetts, Amherst, Nov. 1980.
- ^ Boothroyd, G., "Design for assembly: The Road to Higher productivity", Assembly Engineering, March, 1982.
- ^ Henchy, L.W., "American Manufacturing Fights Back", Business Solutions, Feb. 22, 1988, p.10.
- ^ Assembly Automation and Product Design G. Boothroyd, Marcell Dekker, Inc. 1992
- ^ Product Design for Manufacture and Assembly G. Boothroyd and P. Dewhurst, Boothroyd Dewhurst, Inc. 1989 Marcell Dekker, Inc. 1994
- ^ Design and Analysis of Manufacturing Systems Rajan Suri University of Wisconsin 1995
- ^ Product Design for Assembly: The Methodology Applied G. Lewis and H. Connelly
- ^ Simultaneous Engineering Study of Phase II Injector Assembly line Giddings & Lewis 1997
- ^ "IBM Proprinter Case Study". Engineering Systems Research Center. University of California at Berkeley [1] Archived 2010-07-05 at the Wayback Machine [2] Archived 2006-06-21 at the Wayback Machine
Further information
For more information on Design for Assembly and the subject of Design for Manufacture and Assembly see:
- Boothroyd, G. "Assembly Automation and Product Design, 2nd Edition", Taylor and Francis, Boca Raton, Florida, 2005.
- Boothroyd, G., Dewhurst, P. and Knight, W., "Product Design for Manufacture and Assembly, 2nd Edition", Marcel Dekker, New York, 2002.